Trust your senses! The kefir liquid will Look lighter than it was before the fermentation time. It will smell fresh and may even have a slightly yeasty smell but not a overpowering rotten smell. The Kefir will flow like water and not be thick and slimy. Seasonal changes can be expected, they change in shape and size -even food source preference when the season changes. Healthy kefir grains will convert sugar water into kefir. Don’t consume anything that doesn’t smell or look right. If you suspect that your kefir grains may need some recovery then you can make a new sugar solution and pop them in the fridge for a couple of days up to a week so that they can recover.